Oil composition of improved pour stability



Patented May 4, 1954 OIL COMPOSITION OF IMPROVED POUR STABILITY Orland M. Reiff, Woodbury, N. 3., assignor to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application March 21, 1952, Serial No. 277,910

Claims. 1

This invention relates to lubricating oil compositions. More particularly, it is concerned with oil compositions having stabilized low pour points.

As is well known, the A. S. T. M. pour point of a waxy mineral lubricating oil may be substantially lowered by adding to the oil a small amount of a certain type of chemical agent having waxmodifying properties. Such agents are known as pour point depressants. Oils of low pour point are, of course, highly desirable for use where low temperatures are encountered. Thus, automobile engine oils designed for winter use are generally fortified with pour depressants in order to provide easier starting and better lubrication of the engine parts in cold engines.

A major problem has been encountered, however, in the use or" pour depressants, via, pour point reversion. This is the tendency of an oil, which has had its pour point lowered by the addition of a pour depressant, to revert to a higher pour point when subjected to temperature cycling, as, for example, during winter storage. Thus, an oil containing a pour depressant may have an initial A. S. T. M. pour point of F, but during storage may be found to be solid at temperatures much higher than the original pour point. This tendency for pour point reversion has been found to be particularly pronounced where the pour depressant is of the metal detergent type. This type of pour depressant comprises certain metal salts of organic acids which are available commercially for use in lubricating oils, and which function as detergents as well as pour depressants. The two-fold action of these salts is, of course, highly advantageous. Unfortunately, however, the problem of pour point reversion, which is associated with their use, greatly discounts their value.

It is the object of this invention to provide a practical means of counteracting the our reversion tendency in oil compositions containing these detergent salts as pour depressants, so that the pour points of such compositions are rendered substantially stable.

In accordance with the present invention, we have now found that the pour point of a lubricating oil which has been lowered bythe addition thereto of a detergent salt type pour point depressant may be stabilized by addition to the oil of a small amount of an organic nitrogen compound, particularly an amine and especially secondary and tertiary aliphatic amines. The invention, therefore, comprises the use, in combination, in oil to provide a stable low pour point therein of (1) a minor amount of a metal organic detergent type pour point depressant and (2) a minor amount of an organic nitrogen compound.

The metal organic pour depressant The invention contemplates and is applicable to any metal organic detergent salt having pour depressant properties. Salts of this character are described in detail in previously issued patents of the present inventor, viz., Nos. 2,197,835 and 2,263,445. These salts may be broadly defined as oil-miscible metal organic compounds having a wax-substituted aryl nucleus therein. These include waX-aryl metal oxides, such as metal phenates, metal salts of waX-aryl acids, such as carboxylates and thio-carboxylates, metal salts of wax-hydroxy-aromatic acids, such as waxphenol carboXylat-es, metal salts of wax-aryl sulfonic acids, such as wax-benzene sulfonates and metal salts of wax-aryl amides, as well as other metallo-wax-aryl compounds as shown in previously issued Patent No. 2,197,835. Also included are the sulfur-iced metal salts of the aforesaid types, as disclosed in detail in previously issued Patent No. 2,263,445.

In general, it appears that the metal constituent of the wax-aryl-metallo compound may be any metal. It may be said, however, that metals which are particularly useful as detergent pour depressants in oil belong to the silver, copper, tin, aluminum, iron, alkali and alkaline earth analytical groups, especially the alkaline earth group. The salts of barium are particularly preferred. As non-limiting examples of compounds contemplated herein, the following may be mentioned:

Barium wax-phenol carboxylate Aluminum wax-phenol carboxylate Calcium wax-phenate Lead wax-phenate Barium wax-benzene sulfonate Sulfurized barium wax-phenol carboxylate Zinc wax-benzene sulfonate Basic barium wax-benzene sulfonate Barium wax-naphthalene sulfonate Sodium phenate of wax-phenol disulfide The organic nitrogen compound The organic nitrogen compounds suitable for us in the invention include the following: aliphatic monoand dinitriles, such as acetonitrile and succinonitrile; aromatic nitriles, such as benzonitrile; aliphatic primary, secondary and tertiary monoand diamines, such as monobutylamine, monododecylamine, monooctadecylamine, dibutylamine, didodecylamine, dioctadecylamine, triethylamine, tributylamine, ethylenediamine and tetraethylenepentamine. The aliphatic nitriles and amines may contain substituent groups in the carbon chain thereof, such as hydroxyl, halogen or other groups containing oxygen, ni-

trogen or sulfur, such as a keto, cyano or thio group. Aromatic amines, such as aniline, diphenylamine, naphthylamines and phenylene diamines; C-alkyl derivatives of aromatic amines, such as methylaniline and wax aniline; N-alkyl aromatic amines, such as N-methylaniline, The aromatic amine may contain a substituent group, such as a halogen, hydroxyl or other group containing oxygen, nitrogen or sulfur, without affecting its ability as a pour point stabilizer. Heterocyclic nitrogen compounds are also contemplated, such as pyrrole, pyrazole, aminopyrazole, aminopyridine, aminoquinoline, piperidine, phenothiazine, pyrazoline, pyrazolone, carbazole, thienylethylamine, thienyl nitrile and furoic nitrile. Of the various amines tested, however, the secondary and tertiary aliphatic amines give the best pour stabilizing efiect and these are preferred over the other types of nitrogen compounds.

Although as aforestated, the principle of the invention is applicable to metal organic detergent salt pour depressants in general, it will be illustrated herein by means of the sulfurized barium salt of wax-phenol carboxylate which is typical of the detergent-type pour depressant salts contemplated herein.

Preparation of sulfurized barium wax-phenol carborylate (a) PREPARATION OF \VAX-ALKYLATED PHENOL A parafiin wax melting at approximately 120 F. and predominantly comprised of hydrocarbons, having at least 20 and an average of about 24 carbon atoms in their molecules, is melted and heated to about 200 F., after which chlorine is added until the desired weight (about 14 per cent) is incorporated in the wax. A surficient quantity of this chlorinated wax to provide 3 atomic proportions of chlorine is then heated to a temperature varying from just above its melting point to not over 150 F. On mol of phenol (CGHSOH) is then mixed with the chlorowax. The mixture is then heated to about 150 F. and a quantity of anhydrous aluminum chloride,

corresponding to about 3 per cent of the weight of the chlorowax in the mixture, is slowly added with activ stirring. The rate of addition of the aluminum chloride should be sufiiciently slow to avoid violent foaming and during the addition the temperature should be held at about 150 F. After the aluminum chloride has been added the temperature of the mixture may be increased slowly over a period of from 15 to 25 minutes to a temperature of about 250 F. and then should be more slowly increased to about 350 F. To control the evolution of HCl gas, the temperature of the mixtur is preferably raised from 250 F. to 350 F. at a rate of approximately one degree per minute, the whol heating operation occupying aproximately two hours from the time of adding the aluminum chloride. If the emission of HCl gas has not ceased when the final temperature is reached, the mixture may be held at 350 F. for a short time to allow completion of the reaction. However, to avoid possible cracking of the wax, the mixture should not be heated appreciably above 350 F., nor should it be held at that temperature for any extended length of time.

It is important that all unreacted, or nonalkylated, phenol remaining in the reaction mixture, as well as aluminum chloride, be removed. This can be conveniently effected by washing the product several times with a mixture of water and an alcohol, such as butanol, preferably at elevated temperature, say 175 F. The product may then be treated with steam. This latter step will insure complete removal of the unreacted material and also dry the product.

It will be understood that a wax-substituted phenol prepared according to the above procedure in which a quantity of chlorowax containing three atomic proportions of chlorine and having a chlorine content of 14 per cent is reacted with one mol of phenol, is designated as wax-phenol (3-14). Similarly, wax-phenol -10) and wax-phenol (1-10) may also b prepared by the reaction of suflicient amounts of chlorinated wax, containing 10 per cent by weight of chlorine, to provide 3 atomic proportions and 1 atomic proportion of chlorine per mol of phenol, respectively, in the reaction and are useful in the invention. In general, an amount of chlorowax, containing from about 10 to 18 per cent by weight of chlorine may be used in the reaction to supply between 1 and 4 atomic proportions of chlorine per mol of phenol used.

(0) PREPARATION on THE SULFURIZED BARIUM SALT OF WAX-PHENOL CARBOXYLIC ACID 3-14 Barium oxide is reacted with methanol at room temperature to form a solution of barium methylate. The reaction mixture is then filtered to obtain the pure solution which may contain an amount of barium methylate equivalent to 10 per cent barium by weight.

One hundred grams of Wax phenol, prepared as indicated in (a) is dissolved in 150 grams of mineral oil (8. U. V. 100 sec. at 100 F.) and heated with stirring to 167 E. An amount of the barium methylate solution equivalent to 8.78 grams barium is then added whil allowing the methanol to distill. After stirring for 15 minutes at 167 F., the temperature is gradually increased to 383 F. and CO2 is introduced over a -hour reaction period at 383 to 395 F. The batch is then cooled to 266 F. preparatory to the introduction of elementary sulfur (3.88 grams) which is sprinkled in and the batch stirred for 15 minutes at 266 to 285 F. to insure complete solution of the sulfur. The whole is then cooled to 167 F.

Additional barium methylate, equivalent to 20.2 grams barium, is then added with the simultaneous distillation of methanol. After reacting the mixture 15 minutes, the temperature is gradually raised to 266 F., followed by filtration of the product through filtering clay. The filtrate is then analyzed for barium and diluted with additional mineral oil to have the finished product of 6 per cent barium content.

Pour point stability To demonstrate the ability of the organic nitrogen compounds herein contemplated in stabilizing the pour points of oils containing a pour depressant of the metal detergent type, oil blends of the sulfurized barium salt of wax-phenol carboxylic acid (3-14), both with and without an addednitrogen compound, were prepared and subjected to laboratory temperature cycling tests, the results of which are summarized in Table I. The base oil used in these tests was a Mid-Continent, solvent-refined oil having a kinematic viscosity of 8.39 centistokes at 210 F. and an A. S. T. M. pour point of +25 F. This oil was blended with 1 per cent by weight of a commercial additive consisting of 1 part of the sulfurized barium salt of wax-phenol carboxylic acid (3-14), prepared as described hereinabove, and 1 part of a reaction product of alpha-pinene with phosphorus pentasulflde (antioxidant) This blend had an A. S. T; M. pour point of -25' F. In the table, this oil blend is designated as Blend A. The other blends tested (containing the organic nitrogen compounds) were prepared by simply adding a small amount of the particular organic nitrogen compound to portions of Blend A.

The test procedure involved the-following steps:

1. Fifty-gram samples of the oil blends in standard, tall-form, four-ounce bottles were preheated to 115 F. and then allowed to coolto room temperature;

2. The samples were then cooled to -20 F. over a 22-hour period and maintainedat this temperature for 24 hours.

3. The sampleswere allowed to warm to- +55 F. over a 44-hour period and kept at this temperature for about 4 hours.

4. The samples were finally cooled to -20 F. over a 54-hour period. Theywere observed for fluidity at five-degree intervals beginning with +20 F. during the final cooling stage. In examining the sample for fluidity, it was first tilted slightly. If no flow was observed, the-bottle was tilted to a horizontal position and held for five seconds. The sample was reported as being solid if no flow was observed after this time. The stable pour point is reported as five degrees above the observed solid point.

Certain of the stable. pour points shown in the table are reported as F. which means that these blends were fluid at 15 F. which was the lowest temperature obtained in the final cooling stage of that particular test. Where a final temperature of F; was attained, those blends which still flowed are reported as having stable pour points of 20 F.

It will be seen from the table that whereas the stable pour point obtained for Blend A was +15 E, which amounts to a reversion of 40 degrees (from F), in each of the other blends tested the nitrogen compound inhibited the reversion of the pour point and in certain instances reversion was substantially completely inhibited.

TABLE.POUR POINT STABILITY TESTS Concn. 523

Wt. Percent 9 3 Compound Added To Blend A None +15 Acetonitrile Tributylamine Benzyldimethylamlne 05 5 Ethylenediaminc 10 Tetraethylenepentamine Oleic acid amide of above onoethanolamine 10 p-aminophenol Oetyl pyridinium chloride 05 -10 The amount of the detergent-type pour depressant salt used in the oil is that sufl'icient to substantially lower the pour point of the oil, 1. e., from about 0.05% to about 5% usually about 1.0% by weight. On the other hand, the amount of the organic nitrogen compound required to stabilize the pour point of the oil will be a minor amount, 1. e., from about 0.01% up to about 1% by Weight, although usually from 0.01% to 0.10% is sufficient. In blending certain of the less oilscluble compounds, it is desirableto first prepare a concentrated solution in an alcohol, such as n-butanol, and then blend the desired concentration in the oil.

The pour stabilizing nitrogen compounds of the invention may be added to oils containing other improving agents along with the detergent-type pour depressant, such as anti-oxidants, extreme pressure agents, rust inhibitors, etc.

Concentrated oil blends of the stabilized additives of the invention may be prepared and marketed, such concentrates of the additives providing a readily soluble form of the additive combination for addition to further quantities of oil to improve the pour point characteristics thereof.

Although the invention has been illustrated herein by certain specific examples, it is not intended that the scope thereof be limited thereby in any way, but only as indicated by the appended claims in which it is intended to claim all novelty inherent therein as well as all modifications coming within the scope and spirit of the invention.

W hat is claimed is:

l. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufficient to lower the pour point of said oil, of a metal salt of an organic acid having a wax-substituted aryl nucleus therein and a minor amount, sufiicient to stabilize the lowered pour point of said oil, 01 an organic nitrogen compound selected from the group consisting of unsubstituted nitriles and unsubstituted acyclic amines.

2. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, from about 0.05% to about 2.0% by Weight, of a metal salt of an organic acid having a wax-substituted aryl nucleus therein and a minor amount, from about 0.01% to about 0.5% by Weight, of an organic nitrogen compound selected from the group consisting of unsubstituted nitriles and unsubstituted acyclic amines.

3. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, suflicient to lower the pour point of said oil, of a metal salt of an organic acid having a wax-substituted aryl nucleus therein and a minor amount, suflicient to stabilize the lowered pour point of said oil, of an unsubstituted acyclic amine.

4. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, suificient to lower the pour point of said oil, of a metal salt of an organic acid having a wax-substituted aryl nucleus therein and a minor amount, sufiicient to stabilize the lowered pour point of said oil, of an unsubstituted nitrile.

5. A lubricating oil composition having a sta- 7 bilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, suflicient to lower the pour point of said oil, of a metal salt of a wax-substituted phenol carboxylic acid and a minor amount, sufficient to stabilize the lowered pour point of said oil, of an unsubstituted acyclic amine.

6. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufficient to lower the pour point of said oil, of a metal salt of a wax-substituted phenol and a minor amount, sufficient to stabilize the lowered pour point of said oil, of an unsubstituted acyclic amine.

'7. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, suificient to lower the pour point of said oil, of a metal salt of a wax-substituted aryl sulfonic acid and a minor amount, suificient to stabilize the lowered pour point of said oil, of an unsubstituted acyclic amine.

8. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a Waxy mineral lubricating oil, a minor proportion, suificient to lower the pour point of said oil, of a metal salt of a wax-substituted phenol carboxylic acid and a minor amount, sufficient to stabilize the lowered pour point of said oil, of an unsubstituted nitrile.

9. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufiicient to lower the pour point of said oil, of a metal salt of a wax-substituted phenol and a minor amount, sufiicient to stabilize the lowered pour point of said oil, of an unsubstituted nitrile.

10. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, suflicient to lower the pour point of said oil, of a metal salt of a wax-substituted aryl sulfonic acid and a minor amount, sufficient to stabilize the lowered pour point of said oil, of an unsubstituted nitrile.

11. A lubricating oil composition havin a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufficient to lower the pour point of said oil, of a sulfurized barium salt of a wax substituted phenol carboxylic acid and a minor amount, sufficient to stabilize the lowered pour point of said oil, of dibutylamine.

12. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufiicient to lower the pour point of said oil, of a sulfurized barium salt of a waxsubstituted phenol carboxylic acid and a minor amount, sufficient to stabilize the lowered pour point of said oil, of dioctadecylamine.

' 13. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, suificient to lower the pour point of said oil, of a sulfurized barium salt of a waxsubstituted phenol carboxylic acid and a minor amount, sufficient to stabilize the lowered pour point of said oil, of triethylamine.

14. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufficient to lower the pour point of said oil, of a sulfurized barium salt of a waxsubstituted phenol carboxylic acid and a minor amount, SllfllClSllt to stabilize the lowered pour point of said oil, of ethylenediamine.

15. A lubricating oil composition having a stabilized low pour point comprising a major proportion of a waxy mineral lubricating oil, a minor proportion, sufficient to lower the pour point of said oil, of barium wax phenate and a minor amount, sufiicient to stabilize the lowered pour point of aid oil, of dibutylamine,

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. A LUBRICATING OIL COMPOSITION HAVING A STABILIZED LOW POUR POINT COMPRISING A MAJOR PROPORTION OF A WAXY MINERAL LUBRICATING OIL, A MINOR PROPORTION, SUFFICIENT TO LOWER THE POUR POINT OF SAID OIL, OF A METAL SALT OF AN ORGANIC ACID HAVING A WAX-SUBSTITUTED ARYL NUCLEUS THEREIN AND A MINOR AMOUNT, SUFFICIENT TO STABILIZE THE LOWERED POUR POINT OF SAID OIL, OF AN ORGANIC NITROGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OF UNSUBSTITUTED NIRTILES AND UNSUBSTITUTED ACYLIC AMINES. 